1. FIELD OF INVENTION
The invention relates to a hand-held tool which is used to rotatably drive a bit for fastening, drilling and similar operations, and more particularly to a hand-held tool which has a simple construction and which is more durable and convenient to use than prior art ones.
2. DISCUSSION OF THE RELATED ART
A hand-held tools which is used to rotatably drive a bit for the purpose of fastening, drilling and similar operations by means of a ratchet mechanism, such a ratchet screwdriver, is well known in the art. Referring to FIG. 1, the ratchet mechanism of a ratchet screwdriver includes a hollow body (1) having two notches (1a, 1b) for receiving two constraining plates (2) therein. The hollow body is sleeved on a shaft (3) having a ratchet wheel (3a) mounted thereon. The ratchet shifter (4) is used for depressing the constraining plates (2) to enable one of said constraining plates (2) to engage said ratchet wheel (3a) so as to cause the ratchet wheel to rotate clockwise or counterclockwise. It has been found that the ratchet mechanism of the ratchet screwdriver, functions well when used to rotatably drive a bit for the purpose of fastening or loosening a screw, but said ratchet mechanism also suffers quick wearing of the constraining plates (2) and the ratchet wheel (3a), while because the ratchet wheel (3a) always abuts upon one of the constraining plates and rotates with respect to it. This wear usually allows disengagement of the constraining plates and the ratchet wheel, and may render the entire tool useless.